Continuously indicating radio compass



July 16, 1940. D. G. c. LUCK CONTINUOUSLY INDICATING RADIO COMPASS FiledJune 50, 1938 3 SheetS--Sheel'l l LV NT Lrtorneg RNV, NRV .N .www

`Iuly 16, 1940.

CONTINUOUSLY INDICATING RADIO COMPASS Filed June 30. 1938 3 Sheets-Sheet2 55 'ro .amm/can ,57

7a 7.5 VTV? 75T wl T :inventor David C. LLLC' Lttorneg D. G. c. LUCKv I2,208,378,

July 16, 1940. D. G. c. LUCK CNTINUOUSLY INDICATING RADIO COMPASS I 3Sheets-Sheet 3 Filed June 30, 1938 PEG.

OUTPUT :inventor 4David, G. C. L iJ/C',

Q Gttorneg atente July i6, i940 CONTINUUUSLY INDICATENG )RADIO CONIPASSDavid G. C. Luck, Haddon Heights, N. J., assignor to Radio Corporationof America, a co1'- poration oli Eelaware Application June 30, i938,Serial No. 216,825

8 Claims.

My invention relates to radio direction iinders and more particularly toa radio direction nder which aiords continuous indication throughout itsazimuth.

Numerous types of radio compasses have been disclosed in the prior art.One radio compass is the sci-called left-right type. Such radiocompasses indicate departures to the left or right oi a line toward aradio transmitter. It has if) also been proposed in a copendingapplication oi Alexandre Sev, entitled Direct reading goniorneter,Serial No. i15,899, filed December 15, 1936, to continuously indicatethe bearing of a radio transmitter with respect to a radio rel ceiver.The system proposed by Sev includes a pair of cross loop antennas of thebalanced type and a non-directive antenna In this arrange ment thecurrents from the several loop sections are successively applied throughpairs of diode gc detectors to a common circuit which is also energizedby currents from1 the non-directive antenna. My invention improves theSev system as will hereinafter appear.

It is an object of this invention to provide 25 means for operating acontinuously indicating' radio compass employing a cathode rayindicator. It is a further object of this invention to provide means ina radio compass for deriving electrically scale indications to avoiderrors which 30 might occur in the use of Xed scales. It is a furtherobject of this invention to provide improved means for deriving sideband currents from pairs of directive antennas and carriercurrents from.the non-directive antenna. It is an- 35 other object to provide meansfor applying modulation currents of suitable phase to successivelymodulate currents derived from pairs of directive antennas. Theinvention may be better understood by 40 referring to theaccompanyingdrawings in which Figure l is a schematic diagram of oneembodiment of the invention;

Figure 2 is a circuit diagram of a phase splitting circuit embodied inthe invention; 4,5 Figure 3 is a. circuit diagram showing the circuitfor applying signal and scale impulses to the cathode ray tube;

Figure 4 is a schematic circuit diagram of the balanced modulator; and

Figure 5 illustrates one suitable circuit for the impulse generatorwhich is embodied in the invention.

Referring to Fig. 1, a stable oscillator I, preferably of themagnetostrictive type, is connected 55 to three frequency dividersindicated by reference (Ci. 25d- 11) numerals 3, 5, l, respectively. Theoutputs from the frequency dividers are impressed upon the controlcircuit of a cathode ray tube 9, as will be hereinafter described. Theoutput from the last stage of the frequency divider 'l is impressed uponthe input of a multi-vibrator il, which is connected to a lter it.

The filter output is connected to a pair of phase splitters i5, ll. @neof the phase splitters l5 is connected to the deflecting coils, ordeflecting electrodes, of the cathode ray tube 9. The outputs i9, 2l ofthe second phase splitter Il are connected respectively to a pair ofbalanced modulators 23, 25.

The first balanced modulator is connected to a north antenna and a southantenna. The second balanced modulator 25 is connected to an eastantenna and a west antenna. The several antennas N, E, S, W arepreferably arranged at the corners of a square, as in the Well knownAdcock type direction finders. A non-directive or carrier currentantenna is positioned at the intersection of the diagonals of the squareand is coupled through an amplifier 2 to a radio receiver 29. Theoutputs of the balanced modulators 23, 25 are likewise coupled to theinput of the radio receiver.

Although the invention is not limited to a particular type of receiver,a superheterodyne with a suitable automatic sensitivity control ispreferred. The output of the radio receiver 29 is applied to a phaseshifter and volume control 3|, which is connected to an amplier aridlter 33. The output of the amplifier and filter 33 isapplied to animpulse generator 35 which is connected to the input circuit of thecathode ray tube 9. The radio receiver may also include a loudspeaker31.

The operation of the circuit is essentially as follows: Currents havinga frequency of the order of 36011, .cycles per second are derived fromthe oscillator l and frequency divided to provide impulses at therespective rates of '1211, 361i and 121i cycles per second. Theseimpulses are preferably of different amplitudes 'to provide the scalemarking impulses 39 for the cathode ray tube 9.

The details and operation of the oscillator and frequency dividercircuits are more completely described in U. S. Patent No. 2,121,359,issued June 21, 1938 to David G. C. Luck and Lowell E. Norton andassigned toRadio Corporation of America, or as described irl-Nortonapplication Serial No. 210,574, led May 28, 1938 and assigned to theaforementioned assignee.

es y

The currents from the last stage of the frequency divider 'i areimpressed on the multivibrator to derive therefrom a frequency of 1n, or42% cycles per second. The output currents` from the multi-vibrator,after filtering, are sine wave currents as indicated at 48|. The sinewave currents are applied to the first phase splitter i5 and through thephase splitter to the cathode ray deecting elements. The potentials thusapplied to the deecting elements rotate the cathode ray beam insynchronism with theosclllator and thereby correctly apply the variousscale marking impulses at intervals of 5, l and 30 electrical degrees.

The currents from the second phase splitter operate in synchronism withthe cathode ray beam and modulate, at phase intervals of 90, currentsinduced in the several directive antennas N, E,S and W. The outputcurrents fromV the balanced modulators -are substantially deprived oftheir carrier which is supplied by curents from the carrier antennaafter amplificaion. l Y

The effect of thus successively modulating the several antennas andsupplying carrier currents from the central antenna Vis that of arotating cardioid response pattern. Thus, the rec'eiver output will bemodulated as a. result of the rotation of the cardioid pattern. Thephase of this modulation will depend on the direction from which thereceiver signal arrives. This phase may be shifted so that the northpoint of the cathode ray scale can be made to correspond* to a signalderived from a transmitter due north of the carrier antenna, by use ofthe phase ,l

shifterti. Y

The receiver output .currents may be` further amplified and filtered toattenuate all the currents of undesired frequencies and to applylcurrents of modulation frequency to the impulse generator 35. Theimpulse generator establishes a single impulse 53 whose phase isdetermined with respect to the modulation phase of the receiver output.Thus, the incoming signal establishing thempulse 83 is applied to thecathode ray tube as shown by the marker signal 45.

' v One satisfactory form of phase splitter for aplet plying the'modulation currents to the balanced modulator is shown in Fig. 2. Inthis circut, capacitors di, t@ and resistor 53 are connected in series.The input currents are applied to the junction of capacitor 47 andresistance'53 and to the junction of capacitor 49 and resistance 5|l Theresistive bridge is connected between these same junctions and theremaining junctions of the sexialiy connected capacitors and resistors.The bridge arms are provided with adjustable contacts 55, 5i, 59, 6|,which arerespectively connected to control grids in the balanced modu.lators which-are coupled to the N, W, S, E antennas in the order named.This phase splitting and adjusting circuit has been, found to provide avery satisfactory .means of impressing modulation voltages having therequired phase progression on the four modulator tubes.

One suitable method of applying the deflecting potentials and the signaland scale input potentials to the cathode ray tube is illustrated in`Fig; 3.- The deflecting elements for the cathode ray tube 83 arerepresented as coils 65, 61. It should be understood that the coils arearranged 'in pairs Vand are separated substantially 90.

The first and second anodes 69, are connected VVVto a potentiometer 'inthe output circuit of the ray velocityV modulator tube 1|. The controlgrid tion` of tube |01.

pressed on the input of tube |09 which is prefa capacitorjl to thesignal and scale input which is also connected to the4 ray velocitymodulator tube 1|., The operation of these circuits is more fullydescribed in the above mentioned Norton application.

Referring to Fig. 4, the. thermionic tubes l'l, F9 are connected as abalanced modulator. The modulator currents from the phase splitter tlwhich corresponds to the phase splitter W oi Fig. l are impressed ongrid electrodes t3, 85. The potentiometer 81, -which is connected toscreen grid electrodes 9|, 93, forms a suitable means of balancing themodulator'tubes, which are of the two control grid mixer type. The inputto the modulator tubes is applied through the transformer 95, thesecondary of which is symmetrically connected to control grids of themodulator tubes. Filter circuits 91, 99 are preferably included in theconnections between the grid electrodes 83, 85 and the phase splittercirlcuit di.

One suitable form of impulse generator circuit is show n in Fig. 5. Theinput terminals are connected to an amplifier |03. 'I'he output circuitof the amplifier includes a iiltercircuit |05.

`The output of the filter is connected to a diode rectier which is partof thermionic tube |01. The rectifier is connected to'the amplifier sec-The amplifier` output is imerably a gas discharge typeof tube. Theoutput terminals are indicated by the reference numeral lil. Theforegoing circuit is arranged so that the input sine Wave currents areused to derive the sharply defined impulse marking current. In actualpractice, this circuit' arrangement has proven very satisfactory, but itshould be understood that the invention is not necessarily limited tothe precisefimpulse generator shown.

The operation of the impulse -generator is essentially as follows: Thesignal currents applied to the input IUI are amplified and filtered. Thefiltered signals are applied to the diode rectifier which producesunidirectional currents. The unidirectional currents are madeasymmetrical 'in form by properly choosing the ratio of capacity C and'resistance R in the rectifier circuit. The currents of asymmetrical wave`form are' difier- -entiated by a lter C'R including capacity and Thedifferentiated currents are am- Ypliiied and further differentiated byanother lresistance.

ter C"R". The last mentioned* differentiated currents establish, acrossthe resistor R, potencircuits are known to those skilled in the art,

further description is unnecessary.` Thus, I have described' acontinuously indicating radio compass. The scale markings for thecompass are appliedelectrically and synchronously with the rotation of acathode ray. Signals from a transmitter whose bearing is to bedetermined are modulated in synchronism with the rotation of the cathoderay whereby a signal is derived having a phase dependent upon thebearing of the transmitter. The phase determining this bearing isindicated by applying the received signal to the cathode ray tube.

It should be understood that the non-directive antenna may be omittedandy that the carrier frequency currents may be derived from thedirective antennas. It should also be understood that the system may beoperated by employing a symmetrical rotating field and obtaining twoindications of bearing spaced 180. In such installations there will be a180 ambiguity. A cathode ray tube 63 having deflecting electrodes orcoils disposed as to produce a radial deilection directly may be used,in which case the beam velocity modulator tube 'il is not required.

I claim as my invention:

l. A directive radio receiver including a pairof.

directive antennas, said antennas having response patterns differentlyoriented, a non-directive antenna, a radio receiver, a pair of balancedmodulators, one of said balanced modulators oemg connected between eachof said pair of antennas and said radio receiver, a local source ofmodulation currents, means for applying said modulation currents inquadrature phase to said balanced modulators to successively transferenergy from said directive antennas to said radio receiver so that theresultant response pattern of said directive antennas is eiiectivelyrotated,

' means for applying energy from said non-directive antenna to saidradio receiver, a cathode ray tube, means for obtaining from saidmodulation current source quadrature phase currents for rotating thecathode ray beam of said cathode ray tube. and means for applying asignal to deect said cathode ray as a function of the phase of theoutput signals irom'said receiver.

2. In the device of the character of claim 1 means including saidquadrature phase currents for electrically applying, a compass scale tosaid cathode ray tube.

3. A continuously indicating radio compass including, in combination, apair of directive an tennas, a non-directive antenna, a radio receiver,a pair of balanced modulators respectively connected between said pairsof directive antennas and the input of said radio receiver, a localsource of modulation currents, meansfor obtaining currents of quadraturephase relation from said modulation currents, means for applying saidfor rotating saidcathode ray. and means for ap-v n plying a signalimpulse derivedfrom the output of said radio receiver to deilect saidcathode ray in a radial direction.

4. In a device of the character of claim 3 means operatively related tothe next to the last mentioned means ior applying scale marking impulsesto said cathode ray tube.

5. 'I'he method of continuously indicating the bearing of a radiotransmitter Iwith respect to a radio receiver including a pair o!directive antennas, a non-directive antenna and a cathode ray tube whichincludes impressing radio waves from said transmitter on said antennas,successively modulating energy from each of said directive antennas,combining said modulated energy with carrier frequency energy from saidnon-directive antenna so that the resultant response pattern of saiddirective antennas is effectively rotated, rotating the cathode ray beamof said cathode ray tube in synchronism with the rotation oftheresultant response pattern of said directive antennas, and applyingan impulse derived from said combined energy to deilect and visiblyindicate said cathode ray.

6. A directive radio receiver including a pair of directive antennas,said antennas having response patterns diierently oriented, a radioreceiver, a source of modulation currents, means for obtaining currentsin quadrature phase relation from said modulation currents, means forapplying said quadrature phase currents to successively transfer energyfrom said directive antennas to said radio receiver whereby a rotatingresponse pattern is obtained, a. cathode ray tube, means including saidquadrature phase currents for rotating the cathode ray beam ofsaidcathode ray tube in synchronism with the rotation of said responsepattern,and means for deflecting said cathode ray to provide marks as afunction of the phase of the output signals from said receiver.

7. In a device of the character of claim 6, means including saidquadrature phase currents forelectrically applying in synchronism withthe rotation of said beam a compass scale to said cathode ray tube.

8. A continuously indicating radio compass including, in combination, a,pair of directive antennas, a radio receiver, a pair of balancedmodulators for connecting said directive antennas to the input of saidradio receiver, a source of modulation current, means for deriving twophases from said modulation current source, means for applying saidphases to said pair of modulators whereby a rotating response pattern isobtained, a cathode ray tube, means for applying said phases to rotatethe cathode ray of said tube in synchronism with the rotation of,saidpattern, and means for applying signal impulses derived from the outputof said radio receiver to deect said cathode ray.

DAVID G. C. LUCK.

